Various surgical techniques may be used to repair a diseased or damaged heart valve, such as annuloplasty (contracting the valve annulus), quadrangular resection (narrowing the valve leaflets), commissurotomy (cutting the valve commissures to separate the valve leaflets), or decalcification of valve and annulus tissue. Alternatively, the diseased heart valve may be replaced by a prosthetic valve. Where replacement of a heart valve is indicated, the dysfunctional valve is typically removed and replaced with either a mechanical or tissue valve.
A number of different strategies have been used to repair or replace a defective heart valve. Open-heart valve repair or replacement surgery is a long and tedious procedure and involves a gross thoracotomy, usually in the form of a median sternotomy. In this procedure, a saw or other cutting instrument is used to cut the sternum longitudinally and the two opposing halves of the anterior or ventral portion of the rib cage are spread apart. A large opening into the thoracic cavity is thus created, through which the surgeon may directly visualize and operate upon the heart and other thoracic contents. The patient must typically be placed on cardiopulmonary bypass for the duration of the surgery.
Open-chest valve replacement surgery has the benefit of permitting the direct implantation of the replacement valve at its intended site. This method, however, is highly invasive and often results in significant trauma, risk of complications, as well as an extended hospitalization and painful recovery period for the patient.
Minimally invasive valve replacement procedures have emerged as an alternative to open-chest surgery. Wikipedia Encyclopedia defines a minimally invasive medical procedure as one that is carried out by entering the body through the skin or through a body cavity or anatomical opening, but with the smallest damage possible to these structures. Two types of minimally invasive valve procedures that have emerged are percutaneous valve procedures and trans-apical valve procedures. Percutaneous valve procedures pertain to making small incisions in the skin to allow direct access to peripheral vessels or body channels to insert catheters. Trans-apical valve procedures pertain to making a small incision in or near the apex of a heart to allow valve access. The distinction between percutaneous valve procedures and minimally invasive procedures is also highlighted in a recent position statement of the Society of Thoracic Surgeons (STS), the American Association for Thoracic Surgery (AATS), and the Society for Cardiovascular Angiography and Interventions (SCAI; Vassiliades Jr. TA, Block P C, Cohn L H, Adams D H, Borer J S, Feldman T, Holmes D R, Laskey W K, Lytle B W, Mack M F, Williams D O. The clinical development of percutaneous heart valve technology: a position statement by the Society of Thoracic Surgeons (STS), the American Association for Thoracic Surgery (AATS), and the Society for Cardiovascular Angiography and Interventions (SCAI). J Thorac Cardiovasc Surg. 2005; 129:970-6). Because minimally invasive approaches require smaller incisions, they generally allow for faster patient recovery with less pain and bodily trauma. This, in turn, reduces the medical costs and the overall disruption to the life of the patient.
The use of minimally invasive approaches, however, introduces new complexities to surgery. An inherent difficulty in the minimally invasive percutaneous approach is the limited space that is available within the vasculature. Unlike open heart surgery, percutaneous heart surgery offers a surgical field that is only as large as the diameter of the blood vessel used for access. Consequently, the introduction of tools and prosthetic devices becomes a great deal more complicated as compared to open-chest surgeries. The device must be dimensioned and configured to permit it to be introduced into the vasculature, maneuvered therethrough, and positioned at a desired location. This may involve passage through significant convolutions, at some distance from the initial point of introduction, before placement can be made at the intended site.
Andersen et al. describe a valve prosthesis implanted in a body channel by a way of catheterization in U.S. Pat. Nos. 5,411,442; 5,840,081; 6,168,614; and 6,582,462; and U.S. patent application Ser. No. 10/268,253, hereby incorporated by reference in their entirety. Catheters are hollow flexible tubes which can be passed inside blood vessels to the heart for diagnostic and treatment purposes. The delivery of catheter expanded valves through body channels such as that described by Andersen et al. is thus dependent on instruments of sufficiently small diameters, as well as adequate length and flexibility to navigate blood vessels.
Minimally invasive trans-apical valve replacement procedures have emerged as an alternative to both open-chest surgery and percutaneous valve surgeries. Bergheim et al. present improved methods and systems for cardiac valve delivery in U.S. Patent Application Ser. Nos. 60/702,892 and 10/831,770, hereby incorporated by reference in their entirety. Methods and systems for the repair, removal, and/or replacement of heart valves through the apex of the heart are described. This is an improvement over minimally invasive percutaneous approaches attempting insertion into the vasculature as the trans-apical approach is not limited by the space that is available within the vasculature. Trans-apical delivery is also closer to the heart than catheter-based procedures.
In-vivo studies have shown that catheter-based valve delivery instrumentation may not be well adapted for trans-apical procedures. When inserting balloon catheters, as described in U.S. Pat. No. 6,582,462 and U.S. patent application Ser. No. 10/831,770, it is difficult to steer the balloon and the valve into position resulting from the lack of rigidity and the inherent flexibility of catheters. This is especially true in minimally invasive trans-apical valve procedures. By their very nature, catheters are designed to be long, flexible and bendable to navigate long distances through the vasculature. Catheters are also frequently susceptible to twisting. As a result, catheters are typically thin and made of flexible materials such as plastics or polymers. Catheters are also designed to be disposed on guidewires to better direct the catheter to the correct location. Even so, it is difficult to steadily and accurately deliver tools and devices over long distances. This is especially true in high flow situations such as a beating heart and in places offering the catheters a substantial amount of space to move within. Correct and accurate placement of a heart valve requires both accurate longitudinal positioning as well as rotational positioning. It is important to correctly place the valve as much as possible into a position that mimics that of the native valve to maximize durability and function. It is also important to prevent placement of the valve in a manner that blocks the left and right coronary outflow (as in the case of the aortic valve). There is hence a need to accurately maneuver and steer the valve during implantation. There is also a need for a device that is more suitable for delivering valves during trans-apical procedures.
During balloon-inflation of a flexible leaflet valve, such as a stented tissue valve, it is desired that the valve remain on the balloon until it is firmly positioned at the site of implantation. In the case of balloon-expandable valves, there is hence a need for devices designed to make sure the valve stays on the balloon during inflation.
Bergheim further presents methods and assemblies for distal embolic protection in U.S. patent application Ser. No. 10/938,410, hereby incorporated by reference in its entirety. Here, Bergheim describes distal embolic protection assemblies for use during trans-apical valve surgery. In order to accommodate a distal embolic protection assembly alongside other valve insertion and replacement devices, it is important that the distal embolic protection assembly collapses down to a substantially small diameter to minimize the space it occupies
Macoviak et al. present a filter catheter used to capture potential emboli within the aorta during heart surgery and cardiopulmonary bypass in U.S. patent application Ser. No. 10/108,245, hereby incorporated by reference in its entirety. The filters described by Macoviak are adapted for use during cardiopulmonary bypass, and not during beating heart surgery. The filters described by Macoviak are also intended to be inserted through the femoral artery and further fail to incorporate a temporary valve, useful for capturing large amounts of debris while performing beating heart surgeries. There is hence a need for a filter system better suited for percutaneous and trans-apical valve surgeries.
Accordingly, while open-heart surgery produces beneficial results for many patients, numerous others who might benefit from such surgery are unable or unwilling to undergo the trauma and risks of current techniques. Therefore, what is needed are methods and devices for performing heart valve repair and replacement as well as other procedures within the heart and great vessels of the heart that provide greater ease of access to the heart valves than the current minimally invasive techniques, while at the same time reducing the trauma, risks, recovery time and pain that accompany more invasive techniques.